console.log(Object.prototype.toString.call("foo")); // [object String]
console.log(Object.prototype.toString.call(true)); // [object Boolean]
console.log(Object.prototype.toString.call(1)); // [object Number]
console.log(Object.prototype.toString.call(null)); // [object Null]
console.log(Object.prototype.toString.call(undefined)); // [object Undefined]
console.log(Object.prototype.toString.call({})); // [object Object]
console.log(Object.prototype.toString.call([])); // [object Array]

const isString = () => {};
const isBoolean = () => {};
const isNumber = () => {};
const isNull = () => {};
const isUndefined = () => {};
const isObject = () => {};
